Behrendt Jan H, Taubert Anja, Zahner Horst, Hermosilla Carlos
Institute of Parasitology, Justus Liebig University Giessen, D-35392 Giessen, Germany.
Vet Res Commun. 2008 Apr;32(4):325-32. doi: 10.1007/s11259-007-9033-7. Epub 2007 Dec 25.
Neospora caninum, Toxoplasma gondii and Eimeria bovis are coccidian parasites of veterinary importance. Tachyzoites of N. caninum and T. gondii and sporozoites of E. bovis are able to invade and replicate in endothelial cells in vivo and in vitro. As it holds true for all eukaryotic cells, the survival of parasitized host cells and the parasites themselves should be dependent on ion balances, especially on extra- and intracellular calcium concentrations. Addition of the calcium ionophore A23187 reliably did release merozoites from mature N. caninum and T. gondii meronts grown in cultured primary bovine umbilical vein endothelial cells (BUVEC). Extent and time course of merozoite release depended on both, maturity of the meronts and concentration of the calcium ionophore. Attempts, however, to achieve synchronous release of merozoites from E. bovis first generation meronts by ionophore treatment failed, suggesting a different biological behaviour of this parasite. According to microscopical observations, the quite variable time of E. bovis macromeront maturation and a hampered merozoite exit owing to dense parasite-induced cytoskeleton elements surrounding the meront may be a reason for the lack of inducible synchronous release.
犬新孢子虫、刚地弓形虫和牛艾美耳球虫是具有兽医重要性的球虫寄生虫。犬新孢子虫和刚地弓形虫的速殖子以及牛艾美耳球虫的子孢子能够在体内和体外侵入内皮细胞并在其中复制。正如所有真核细胞一样，被寄生的宿主细胞和寄生虫本身的存活应该依赖于离子平衡，特别是细胞外和细胞内的钙浓度。添加钙离子载体A23187确实能可靠地从培养的原代牛脐静脉内皮细胞（BUVEC）中生长的成熟犬新孢子虫和刚地弓形虫裂殖体中释放出裂殖子。裂殖子释放的程度和时间进程取决于裂殖体的成熟度和钙离子载体的浓度。然而，试图通过离子载体处理使牛艾美耳球虫第一代裂殖体同步释放裂殖子的尝试失败了，这表明该寄生虫具有不同的生物学行为。根据显微镜观察，牛艾美耳球虫大裂殖体成熟时间差异很大，并且由于裂殖体周围密集的寄生虫诱导的细胞骨架成分阻碍了裂殖子的排出，这可能是缺乏诱导性同步释放的原因。
